Airless thermal regenerator or enhancer with mixer

ABSTRACT

A combustor comprises a fuel-fired burner for a vehicle application. In one example, the fuel-fired burner is configured to regenerate a particulate filter where the fuel-fired burner comprises one of a thermal regenerator or thermal enhancer that operates with airless fuel injection. A fuel nozzle supplies fuel to the fuel-fired burner and an igniter ignites fuel sprayed from the fuel nozzle. A mixer is positioned downstream of the fuel nozzle and upstream of the igniter and operates to reduce fuel droplet size, which improves ignition.

TECHNICAL FIELD

The subject invention relates to a fuel-fired burner for a mobile application, and more particularly to a vehicle exhaust system utilizing a thermal regenerator or enhancer that has a mixer.

BACKGROUND OF THE INVENTION

Exhaust systems are widely known and used with combustion engines. Some exhaust systems utilize a thermal regenerator (TR) or a thermal enhancer (TE). A TR is an active unit that enables regeneration of a diesel particulate filter (DPF) as well as providing exhaust thermal management under various operating conditions. A TE is a partial range burner supporting active DPF regeneration or exhaust thermal management. The TE elevates the exhaust temperature of exhaust gas to enable regeneration of a DPF under low temperature conditions or to improve the efficiency of NOx reduction catalysts.

The TR and TE include a combustor unit that includes an air supply line, a fuel supply line and an igniter unit. This traditional configuration is disadvantageous from a cost and complexity perspective. Airless TRs and TEs are desirable because they reduce cost and are less complex due to the elimination of the air supply components. However, airless TRs and TEs have significantly larger fuel droplet sizes, which are difficult to ignite and produce more hydrocarbons.

SUMMARY OF THE INVENTION

A component assembly includes a combustor that comprises a fuel-fired burner for a mobile application. In one example, the fuel-fired burner comprises one of a thermal regenerator or airless thermal enhancer operating with airless injection and which is configured to regenerate a particulate filter. A mixer is positioned within the thermal regenerator or enhancer to improve ignition by reducing fuel droplet size. A low pressure region is also created behind the mixer which further assists the ignition process.

In one example, at least one fuel nozzle supplies fuel to the combustor and an igniter ignites fuel sprayed from the fuel nozzle. The mixer is positioned downstream of the fuel nozzle and upstream of the igniter and operates to reduce fuel droplet size as fuel flows through the mixer. Fuel from the fuel nozzle is solely mixed with existing exhaust gases for ignition without requiring an additional atomization air supply.

These and other features of the present invention can be best understood from the following specification and drawings, the following of which is a brief description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a cross-sectional view of a combustor as used with a thermal regenerator or thermal enhancer.

FIG. 2 is a schematic view of a mixer positioned within the combustor.

FIG. 3 is a schematic view of another example combustor and mixer.

FIG. 4 is one example of a mixer.

FIG. 5 is another example of a mixer.

FIG. 6 is another example of a mixer.

FIG. 7 is another example of a mixer.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 shows an exhaust component assembly 10 with a combustor 12. The combustor 12 comprises any type of combustor where air-assisted fuel injection is replaced by airless injection. Examples of such combustors would include vehicle exhaust after treatment components, auxiliary vehicle passenger compartment heaters, turbine combustors, etc.

The exhaust component assembly 10 includes a housing 14 defining an internal cavity 16 and an internal wall structure 18 that defines a combustion chamber 20. The housing 14 includes an exhaust gas inlet 22 and an exhaust gas outlet 24. Exhaust gases generated from an engine E flows through any upstream exhaust components 26 to the exhaust gas inlet 22. Exhaust gases flow through the exhaust component assembly 10 to the exhaust gas outlet 24 and then on to downstream exhaust system components 28.

At least one fuel nozzle 30 is supported by the housing 14 to inject/spray fuel from a fuel supply 32 into the combustion chamber 20. The fuel is sprayed into existing exhaust gases within the combustion chamber and an igniter 34 (FIG. 2) then ignites the fuel to increase heat. In one example, the igniter 34 comprises one or more electrodes 34 a, 34 b; however, other types of igniters could also be used.

The exhaust component assembly 10 comprises a fuel-fired burner. In one example, the fuel-fired burner comprises one of an thermal regenerator (TR) or thermal enhancer (TE). A TR is an active unit that enables regeneration of a diesel particulate filter (DPF) as well as providing exhaust thermal management under various operating conditions. A TE is a partial range burner supporting active DPF regeneration or exhaust thermal management. The TE elevates the exhaust temperature of exhaust gas to enable regeneration of a DPF under low temperature conditions or to improve the efficiency of NOx reduction catalysts. Further, a TR comprises a combustor system that operates overall an entire engage map while a TE typically operates only in low and medium speed load ranges.

The igniter 34 ignites fuel droplets sprayed by the fuel nozzle 30 in one of the TR or TE to increase temperatures such that a particulate filter PF can be regenerated or a NOx reduction catalyst can be heated up. Ignition of the fuel accomplished without any type of additional atomization air supply to the combustor 12. This provides reduced cost and complexity of the component assembly.

FIG. 2 shows a TR/TE that incorporates a mixer 40 to improve ignition. In the airless configurations discussed above, fuel sprayed by the nozzle tends to include large droplet spray 42. The mixer 40 is positioned within the TR/TE downstream of the fuel nozzle 30 and upstream of the igniter 34. The mixer 40 is defined by an outer peripheral surface 44 with a downstream end face 46 and an upstream end face 48. The downstream 46 and upstream 48 end faces provide discontinuous surfaces that cooperate to reduce the size of fuel droplets flowing through the mixer 40 from the upstream end face 46 to the downstream end face 48. Fuel exiting the mixer 40 is comprised of a fine mist (very small droplets) as indicated at 50. This mist 50 is significantly easier to ignite than the large droplet spray 42.

Examples of different mixers 40 are shown in FIGS. 4-7. FIG. 4 shows an example of a wire mesh mixer 40a having an outer ring 52 with wire mesh supported within the ring 52 to provide the discontinuous surfaces at the upstream 48 and downstream 46 end surfaces.

FIG. 5 shows an example of a vane mixer 40b having an outer ring 54 and cross-members 56 that support a plurality of vanes 58. The vanes are orientated at various different angles and positions to provide the discontinuous surfaces at the upstream 48 and downstream 46 end surfaces.

FIG. 6 shows an example of a commercial mixer 40c that includes an upper member 60, a lower member 62, and a center plate 64 positioned between the upper 60 and lower 62 members. The upper member 60, lower member 62, and center plate 64 include various contoured surfaces 66 and removed sections 68 that cooperate to provide the discontinuous surfaces at the upstream 48 and downstream 46 end surfaces.

FIG. 7 shows an example of a mixer baffler 40d that includes a large plate portion 70 with an opening 72, a small plate portion 74, and a plurality of connecting members 76 that connect the large plate portion 70 to the small plate portion 74. The connecting members 76 extend in different directions and at different angles to provide the discontinuous surfaces at the upstream 48 and downstream 46 end surfaces.

It should be understood that the examples set forth in FIGS. 4-7 are not the only mixers that can be utilized within the TR/TE. Any type of mixer element could be used. Further, any of the mixers shown can be used in either the TE or TR and can be used in any of the different exhaust inlet/outlet configurations, which will be discussed below.

FIG. 1 shows one example exhaust inlet/outlet configuration. In this example, the internal wall structure 18 is connected at one end to the housing 14 with a first end plate 80 and is connected at an opposite end to the housing 14 with an enlarged shroud 82. The fuel nozzle 30 extends through the first end plate 80 into the combustion chamber 20. The fuel nozzle 30 defines a nozzle axis A1 that extends along a length of the fuel nozzle 30. The exhaust gas inlet 22 is mounted through a wall of the housing 14 at a position between the first end plate 80 and the shroud 82. The exhaust gas inlet 22 defines an exhaust gas flow axis A2 that is non-parallel to the nozzle axis A1.

Exhaust gas enters through the inlet 22 and hits an outer surface of the internal wall structure 18, which include a plurality of openings 84 that allow exhaust gas to enter the combustion chamber 20. The mixer 40 mixes the exhaust gas and the fuel droplets to produce the mist that is ignited by the igniter 34. As discussed above, this occurs without any additional air supply to the combustion chamber 20. Exhaust gas then flows from the combustion chamber, and/or through openings 86 in the shroud 82, to the exhaust gas outlet 24.

FIG. 3 shows another example inlet/outlet configuration. In this example, the nozzle axis A1 and the exhaust gas flow axis A2 are parallel to each other. As such, the exhaust gas inlet 22 is positioned at the same end as the fuel nozzle 30. It should be understood FIGS. 1 and 3 are only examples, and that other inlet/outlet configurations could also be used.

In any of the configurations discussed above, the mixer 40 serves to significantly reduce the size of fuel droplets within the combustion chamber 20. These smaller droplets are more easily mixed with the exhaust gases, and are therefore easier to ignite. In addition, by positioning the mixer 40 downstream of the fuel nozzle 30 and upstream of the igniter 34, a lower pressure region is created at the upstream side of the mixer that also improves ignition and flame stability.

Although an embodiment of this invention has been disclosed, a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of this invention. For that reason, the following claims should be studied to determine the true scope and content of this invention. 

1. A component assembly comprising: a combustor comprising a fuel-fired burner having airless fuel injection; at least one fuel nozzle to supply fuel to said combustor; an igniter to ignite fuel sprayed from said at least one fuel nozzle; and a mixer positioned downstream of said at least one fuel nozzle and upstream of said igniter.
 2. The component assembly according to claim 1 wherein said fuel-fired burner comprises one of a thermal regenerator or thermal enhancer.
 3. The component assembly according to claim 2 wherein said fuel-fired burner is configured to regenerate a particulate filter.
 4. The component assembly according to claim 1 wherein said mixer solely mixes fuel with existing exhaust gases for ignition without requiring an additional atomization air supply.
 5. The component assembly according to claim 1 including a housing having an exhaust gas inlet, an exhaust gas outlet, and an internal wall structure positioned within said housing to define a combustion chamber, and wherein said mixer is supported by said internal wall structure within said combustion chamber.
 6. The component assembly according to claim 5 wherein said at least one fuel nozzle defines a nozzle axis extending along a length of said at least one fuel nozzle, and wherein said exhaust gas inlet defines an exhaust gas flow axis that is non-parallel to said nozzle axis.
 7. The component assembly according to claim 5 wherein said at least one fuel nozzle defines a nozzle axis extending along a length of said at least one fuel nozzle, and wherein said exhaust gas inlet defines an exhaust gas flow axis that is parallel to said nozzle axis.
 8. The component assembly according to claim 5 wherein said at least one fuel nozzle defines a nozzle axis extending along a length of said at least one fuel nozzle and wherein said mixer is axially spaced from a tip of said at least one fuel nozzle along said nozzle axis and said igniter is axially spaced from said mixer along said nozzle axis.
 9. The component assembly according to claim 1 wherein said igniter comprises at least one electrode positioned downstream of said mixer.
 10. The component assembly according to claim 1 wherein said mixer is defined by an outer peripheral surface with a downstream end face and an upstream end face, and wherein said downstream and upstream end faces provide discontinuous surfaces that cooperate to reduce the size of fuel droplets flowing through said mixer from said upstream end face to said downstream end face.
 11. The component assembly according to claim 1 wherein said fuel-fired burner is configured to heat up a NOx reduction catalyst.
 12. A method of assembling a component comprising the steps of: (a) providing a combustor comprising a fuel-fired burner having airless fuel injection, providing at least one fuel nozzle to supply fuel to the combustor, and providing an igniter to ignite fuel sprayed from the at least one fuel nozzle; and (b) positioning a mixer within the combustor downstream of the at least one fuel nozzle and upstream of the igniter.
 13. The method according to claim 12 including solely mixing fuel with existing exhaust gases for ignition without requiring an additional atomization air supply.
 14. The method according to claim 12 including providing a housing having an exhaust gas inlet, an exhaust gas outlet, and an internal wall structure positioned within the housing that defines a combustion chamber, and including supporting the mixer on the internal wall structure within the combustion chamber.
 15. The method according to claim 12 including forming the mixer to be defined by an outer peripheral surface with a downstream end face and an upstream end face with each of the upstream and downstream end faces providing discontinuous surfaces that cooperate to reduce the size of fuel droplets flowing through the mixer from the upstream end face to the downstream end face.
 16. The method according to claim 12 wherein the fuel-fired burner comprises one of a thermal regenerator or thermal enhancer.
 17. The method according to claim 16 including configuration the fuel-fired burner to regenerate a particulate filter. 